Protection circuit board 24v liion

hello
I am having some trouble with a custom battery-pack for a big flashlight, in fact it is for a 200w hmi (underwater use). Because of powerconsumption I had to change the pcb to a bigger one, but after changing the charger shows that it is fully charged all the time, the voltage reads only aboute 8v aswell…. any ideas here, do anyone know these boards?



What is your battery pack cell configuration— are you using 6 18650 cells in series to get 24 volts? How many in parallel?

i have studied these type of circuit boards in various devices. The board in the bottom photos appears very similar to those used in hoverboard cell monitoring boards. They have a simple monitoring function with a protection feature that opens the pack circuit to disable it in the event of over- or under- voltage conditions, and it has a very slow bleed-off feature for balancing or draining a pack.

If the pack is too low (out of range) then the protection circuit prevents charging as a safety feature.

You need to use a voltmeter to measure each cell voltage individually—the pack measurement may not be correct if the protection is activated.

6s5p batterypack

it is this pcb;
http://www.ebay.com/itm/5-6-or-7-cells-20A-w-balancing-Li-ion-Lithium-18650-Battery-In-Out-Protection-/111091669495

Procedure:

  1. Connect your 7 cells in series (cells should be identical) (or for 14 cells: 2cells parallel, 7 cells in series) etc.
  2. Then connect ve of the cells to B, then to B6, B5, B4, B3, B2, B1, B+ (B+ should be left opened for 6cells, B+ and B1 should be left open for 5cells)
  3. Activate the circuit by charging to P+ and P- using Constant current/Constant voltage charger.

for my batterypack just insulated B+ and left it unused….

What a confusing and screwed-up numbering system. That’s what happens when vendors try to copy (steal) designs that they don’t understand.
i can’t see all the labels, but it appears that the previous board was referencing voltage and cell ID#'s from the top most voltage on down starting with the number 1, where cell #1 “+ve” = “B+”, and the wiring connections to the boards were made from the bottom of each cell -ve end, B1-, B2-, etc. With a 6s5p pack, then the “-ve” end of the bottom-most cell #6, B6, connects to the “B-” pad. There were 4 heavy gauge wires B+/-, P+/-, and 5 skinny wires.
One problem is that the new board starts counting at 0, but they left it off the schematic, labelling it “B+” on the J1 terminal block. Also it is referencing voltages from the bottom-most voltage going up and the terminal references and connections are made on the top +ve end of each cell.
So as before the heavy wire from the bottom of the pack connects to the B- pad, but the top of that bottom-most cell is labelled “B6” regardless of how many cells in your series string. So you would need to connect the old “B5-” wire to “B6” on J1, and continue on up J1 with the skinny wires. This will fill B6 thru B2 on J1 with the 5 skinny wires. Then you will need to add another skinny jumper wire from the old heavy B+ wire to the “B1” terminal. The end of old B+ wire must also be connected to the old P+ wire in order to get the positive voltage terminal out to the Pack connector
The low side of the pack is switched on/off by the 4 big FETs on the board in order to open circuit the pack for protection. It looks to be clear where the big heavy B- and P- wires get soldered to the pads on the board.
Hope this helps, if not ask questions, good luck and be careful…

What a freakin' mess.
In your new BMS, you are to connect your pack's rearest cell arse to B-, then next buttock (at first cell head potential) at B6, next to B5, then B4… until B2, then the topmost cell's cathode/head goes into B1 (B+ is not connected as B1/B+ is the last segment for 7-cell configuration, unused in your case as it is said in the BMS' eBay ad).
If you bought the board pre-configured for 6-cell operation, it should work straight this way. If not, you'll need to do some modification to the board, ask the seller (also claimed in the eBay ad). This has to do with the fact that these battery management boards get the power they need to operate from the pack's cathode, which in a lesser amount of cells config is not connected to the topmost “lead”, B+.
Use a voltmeter to identify the voltage differential points of the pack. If the pack is about balanced, you'll read around the same voltage difference between each step (serial battery segment).

Take/feed power straight from the pack's cathode and from the board's output, P-.

Soooo what I dis were kindof super-wrong?

Well, if you had it done right from the start more than probably you may not have opened this thread. Everything has an underlying reason… ;-)

Mmm, you said 200W light? That means current can go up to 10+A from the pack. Recommendation: increase the gauge of the B-/P- wiring, to at least a pair of AWG18s (≈AWG15) in and out, to be safe and minimize losses.

Cheers ^:)

so this is how i should wire it….? and the B+ from the old PCB goes directly to the pack/charge in/plus out?

comment deleted

Sorry kennybobby, with all due respect, no need to add more fuel to this insanely confused BMS fire.

  1. The P- wire is there, up right position in the photo. That is the pack's low side output.
  2. The P+ wire here is an illusion. Battery management systems either switch the battery's current flow by the low side (common) or by the high side. In BMSs with P+ there's nothing between it and B+ (direct connection). Good to see the new BMS has no P+ lead, its misleading. Corollary: the B+ lead carries no significant amount of power, only what is required for the BMS logic to work, so a regular thin wire is allright.
  3. B+ goes into the B1 pin of the new BMS and no jumper wire to B+, unless esmi183 were to have been instructed to do so with additional directions from the eBay seller to convert the pack from 7S to 6S operation. This does not seem to be the case, though esmi183 still hasn't made clear if his new BMS came 6S pre-configured.

Your rewiring seems right, esmi183. Of course, if I were you I would use a multimeter to determine the battery segments. B6- (= B-), P+ in the middle… whoever designed the layout and labeling of that old BMS needs a nice spanking. :facepalm:

Thanks, you are a champ! :slight_smile:

The instructions only say that if i want to use it as a 6s I will need to forget the b+ wire, I have done nothing to it, and they have not either…. the seller gave me the impression that it ere fine as it were, but maby not?

I would just let you guys know that I really much apriciate your help, I apriciate it as much as I do not like talking to the china-guy selling me this crap, nobody knows how to modify the BMS to work with 6cells.

I am sure I got the connections right this time, much thanks to you guys :slight_smile: But the BMS still does not work…. soooo do not buy cheap crap from crap vendors that do not know what they are selling :wink:

If anyone knows how to modify it, please let me know….

Sorry for your troubles. i found that same unit on ebay and went ahead and ordered one, that way i can trace the schematic to actually see how the circuit is supposed to work. U22 looks like a Texas Instruments cell monitoring chip, but where does it get it’s power…? that may be why it is not working, since it controls the drive for the FETs and for balancing. It has been shipped, so should come in any week now…

wow thats more than expected :slight_smile: thanks

okay i got the board and traced it out. They are taking power to the logic chip, a CD4011 quad 2-input NAND gate, and to the power rails of the opto-coupler strings, from pin 4 of J1, labelled as either “B3” or “3” depending upon the vendor, thru a 10k resistor located underneath the U17 opto-coupler.

So you will need to solder some small jumper wires to get power to the opto rails as shown below on the back side of the board. i like to use 30AWG wire-wrap to make these sort of solder repairs—wrap it around the pin and touch it with a hot iron and add a tiny bit of solder.

Also you may want to inspect and touch up some of the solder joints on both sides of the rest of the board—i noticed it was pretty sloppy and some joints looked inadequate. Not sure if they used solder barrels on thru holes, trying for low cost…

Good luck, let us know how it goes.

wow
I will defently try this, and I will defently let you guys (and girls maby) know haw this works out for me! thanks!

Mmmkay, I guess the board wasn't ordered pre-configured for 6-cell operation.

It may have to do with some onboard resistor value modifications (?).

Ask the seller (wkws20). Try something like “6-cell board mod please?”.

Cheers

The listing indicates no components needed to change to 5S or 6S, and i have verified that by tracing the circuits.

The inputs (pin1) to the opto couplers (EL817) are driven by the cell monitoring chips (DW01) on the backside of the board; the outputs are connected in a serial string that becomes the gate drive for the FETs—if any DW01 detects an over-charge or over-discharge condition, it will interrupt the string and the FETs will be turned off.

The opto strings start at pin 4 of the topmost devices; so these jumpers are needed to bypass the unused optos and get power to the active portions of the serial strings. This board could be used with 4S- to 7S-cell packs by adding the appropriate jumpers.

Balancing is done on the front side of the board thru the 51 Ohm resistors and the TL431 shunt regulator chips. The balancing voltage is set by resistors in a voltage divider that i calculated to turn on balancing when the cell is above 4.183vdc.

flag: 7S 20A cell protection board with balancing